214 ANNUAL OF SCIENTIFIC DISCOVERY. 



IMPROVEMENT IN LIGHT HOUSES. 



The following is an abstract of a paper upon the above subject recently 

 read before the Society of Civil Engineers (Eng.) by Mr. Herbert :. 



The floating sea-marks, as ordinarily constructed, labored under these 

 several defects of riding uneasily on the waves, of being frequently sub- 

 merged, and also of being carried away from the mooring chain being broken, 

 not an uncommon occurrence in heavy weather. To obviate these defects 

 a wrought iron pear-shaped buoy was proposed, of a circular form in plan, 

 the centre of gravity being placed a little below the water floating line; 

 the bottom was made concave, being indented internally in the form of a 

 cone, to the apex of which the mooring chain was attached. An experiment 

 made with one nine feet in height, six feet six inches in diameter, and 

 submerged to the extent of two feet, presented under all circumstances of 

 wind and tide an upright body seven feet out of the water; the power 

 of retaining a vertical position arose from the tide or wave acting simultane- 

 ously, and with almost equal force, on the exterior of the buoy and the 

 interior of the cone. It is now proposed to have floating light houses upon 

 this principle of construction. The security of such light towers would of 

 course depend upon the moorings. Now, from observations made at Bishop's 

 Rock, the most westerly of the Scilly group, it was ascertained that of waves 

 measured from the hollow to the unbroken crest those which had a height of 8 

 feet were in number thirty-five in one mile, and eight per minute ; of 1 5 feet, 

 five or six in a mile, and five per minute ; of 20 feet, three in one mile, 

 and four per minute ; and it was calculated that, with moorings sufficiently 

 strong, neither the pressure of the wind nor the action of the waves would 

 cause any inconvenience upon any sea light tower on this construction. The 

 present light houses could be placed only to act as warning points to mariners, 

 whereas these fca light towers might be advantageously employed as "guid- 

 ing" or " fair way" lights. Of course these beacons could be placed in almost 

 any and every position, and would thus "form a new era in the system of 

 lighting, at once double the safety of navigation, and be the means of saving 

 many valuable lives." There was also this very important consideration, as 

 contrasted with light houses, that the expense was very materially less, and 

 the time required for construction and mooring would be very much lessened. 

 For instance, the light house on the Skerry-vore Rock occupied seven years 

 in building, and cost upwards of 90,000; whereas, by means of the sea 

 light tower, the same object might be accomplished, in one year, at a cost of 

 30,000. These new forms would also possess the advantage of being acces- 

 sible in all weathers. If this principle of construction proves to be correct, it 

 would be evidently applicable for floating forts, and to almost every other 

 description of stationary floating bodies. 



One of the most brilliant results of the "World's Fair at London, was a book 

 upon it, by Charles Babbage. Among the chapters of that work is one 

 devoted to light houses and their improvement, and containing the general 

 principles and many details of a most admirable system for distinguishing 

 lights by causing them to show their numbers by rapid eclipses and flashes 



